Your Guide to Operable Wall Louvers
by Kristi Duce, CCS, GGP, CSI, AIA, NCARB
Operable wall louvers are ideal for controlling airflow and offer maximum flexibility in terms of design, performance, and functionality. To control airflow, "adjustable" wall louvers contain blades that typically rotate within the louver frame between fully open at a preset angle and fully closed. In some cases, the operable blades may be the only set of blades within the louver frame. However, in dual-blade operable or "combination" louvers, the rotating blades are in addition to the set of fixed blades.
If climate conditions preclude the use of single louvers, dual-blade operable units allow aesthetic needs to be met while maintaining functionality and weather protection. If aesthetics is a concern due to the high visibility of a louver, a dual-blade unit with a fixed louver on the exterior can offer consistent appearance regardless of the interior blade’s position.
When severe weather is a concern, operable louvers should not be specified as a single unit, as they typically cannot withstand windborne-debris impact and are ineffective at resisting wind-driven rain. Instead, one can opt for a dual-blade model with a fixed louver capable of enduring these conditions on the exterior, and an operable blade on the interior for airflow control.
If the operable louver location makes security a concern, a dual-blade louver can be used with a fixed-blade louver on the exterior attached with security screws or concealed fasteners. Several other combinations of dual-blade louvers are available, or one can be created by using any type of fixed blades combined with operable blades in the same frame.
The blades on operable louvers can be operated by cranks, push bars, chains, or actuator devices that are electrically, pneumatically, or hydraulically powered. The louver location and function generally dictate the operation type required.
Operable louvers can be drainable-blade or non-drainable-blade. The former is designed with gutters to collect water falling on the blade and drain it to the blade ends. There, it flows in the channels of vertical frame members to the bottom of the louver and is weeped to the exterior. Non-drainable blades, on the other hand, allow the water falling on the blade to flow down its face to the louver face and then drip off—frequently to be blown onto the blade below.
Operable louver performance is measured by the following factors:
- free area (i.e., area through which air can pass; that is, the total of the spaces between blades multiplied by the distance between jambs)
- air-performance testing (i.e., the resistance of the louver to the air flowing through it—the static-pressure drop through the louver is measured for a set of airflow velocities through the free area)
- water-penetration testing (i.e., the weight of water in grams per square meter [ounces per square foot] of free area passing from the louver’s exterior to the interior at various air-intake velocities)
- air-leakage testing in the closed position (i.e., the volume of air per unit of face area passing through the louver at a specified pressure differential, with a stated torque holding the device in a closed position)
Energy performance is also a growing concern. To address this, some manufacturers offer insulated blades or louvers with thermally broken blades and frames, along with blade-edge and blade-jamb seals.
Galvanized-steel sheet and aluminum extrusions are the most commonly used materials for louver blades and frames. The latter is a popular choice because of its appearance, good corrosion resistance, and low fabrication cost. Other metal options include stainless steel, copper, lead-coated copper, brass, and bronze. Depending on the material, various finishes for operable louvers are also available.